1. Field of the Invention
This invention relates to machines of the type which are utilized for removing dents and distortions from tubular pipe by mechanical pressure exerted against the internal walls thereof.
2. Brief Description of the Prior Art
As a result of the need to extend the useful service life of various types of pipe, rather than replacing damaged pipe sections with entirely new pipe, many types of apparatus have been devised for maintaining pipe by removing dents and other anomalies which may be developed in the pipe during usage, and which may impair the ability of the pipe to convey fluids efficiently. Among a number of prior patented structures which undertake to accomplish this function, and restore pipe to its undistorted dent-free condition, are those structures shown in Long U.S. Pat. No. 2,341,278, Perkins U.S. Pat. No. 2,787,763, McCown U.S. Pat. No. 2,780,122, and Priester U.S. Pat. No. 3,817,079. In the Perkins apparatus, a section of pipe from which dents and other anomalies are to be removed is moved to a position in which it surrounds a scissor type extension structure which moves semi-cylindrical forms radially outwardly against the internal walls of the pipe to press out and remove dents and distortions. The semi-cylindrical external surface of each of the forms or shoes provided in the Perkins structure for contacting and bearing against the internal walls of the pipe is formed on a radius of curvature which is larger than the radius of curvature of the pipe. Other generally similar structures which have been provided in the prior art have a similar relationship of these radii of curvature, or else provide pressure shoes or forms which are of the same radius of curvature at the external surface thereof as the radius of curvature of the internal wall of the pipe.
It is a widespread practice in apparatus of the type used for removing dents and anomalies from pipe by the radially outward movement of internally positioned shoes or anvils to actuate these shoes by means of pneumatic or hydraulic power fluids. Further, in some pipe straightening systems, carriage or conveyance subassemblies are provided for supporting long lengths of pipe and moving such pipe sections into a position around the shoes or anvils used to remove dents from the pipe.